Electromagnetic device



H. LlsT ELECTROMAGNETI C DEVICE Filed April 5, 1938 2 Sheets-Sheet 1 Oct. l, 1940. H. Llsr ELECTROMAGNETIC DEVICE Filed April 5, 195s 2 Sheets-Sheet 2 Patented Oct. l, 1940 w UNITED' STATES PATENT OFFICE Application April 5, 1938, Serial No. 200,066 In Germany December 30, 1936 8 Claims.

This invention relates to an electromagnetic device of which the armature is turnable to-andfro.

An object of the invention is to make certain improvements in such an electromagnetic device whereby the capacity thereof for transmitting power will be increased without adding to its size and weight.

Another object is to provide in such a device a stator of pot formation, with an axial core on which the field winding is put and which preferably extends from the base of the pot-form stator in the manner of a yarn-bobbin.

Another object is to provide in such a. device an armature of disc-like formation mounted to turn to-and-fro in the stator, the stator and the armature Ato be respectively provided with toothlike pole-projections and to be so dimensioned that their ux-conducting portions are of equal or nearl-y equal cross-sectional areas.

Another object is to provide a construction of such a device in which the last-mentioned crosssectional areas are suillciently large to ensure that the stator and armature will not reach their magnetic saturation limit in the operation oi' the device. By virtue of such a construction, undesirable straying of the magnetic ilux from the said flux-conducting portions will be materially reduced or avoided.

Yet another object is to reduce or avoid straying of the ilux from the ileld winding by making the cross-sectional form of the winding circular or square or varying only slightly from circular or square. Such a cross-sectional form is desirable because the peripheral or external surface is small in relation to the cross-sectional area. Theoretically, a circular cross-section is the ideal, but in practice it will usually be found that a square, or nearly square, cross-section is the nearest available approximation to the ideal.

Various other objects of the invention will be apparent from the following specification and claims.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig l is a sectional elevation illustrating one form of the toothlike pole-projections.

Figs. 2 and 3 are fragmentary sections illustrating modied forms of pole-projections.

Fig. 4 is a section ofan electromagnetic device in combination with a multi-contact relay which is actuated by the device, and Fig. 5 is a corresponding perspective view drawn to a smaller scale.

(Cl. F15-336) Figs. 6 and 7 are .sections of modiiled constructions of the electromagnetic device, Fig. 'I being a section on the plane indicated by the line VII- VII of Fig. 8, which is an elevation of the main body of the electromagnetic device and a section of a cover-plate shown removed.

Fig. 9 illustrates a constructional detail to a large scale.

Figs. 10 and l1 are views corresponding to Figs. 6 and 'I but illustrating further modifications.

Figs. 12 and 13 are diagrammatic sectional views illustrating forms of winding wire. l

Throughout the drawings, similar or corresponding parts are denoted by the same refer-v ence numerals.

In the construction according to Fig. 1, the stator I and the armature 8 are each provided with eight pole-projections, hereinafter called poles for simplicity in referring to the drawings. The stator poles are denoted by I1 and the armature poles by 9. Each of these poles is constituted by a radially projecting portion. The number of poles employed can be chosen in accordance with the purpose to which the device is to be applied, consideration being given to the angle through which it is desired to turn the armature to-and-fro in the operation of the device. The armature would be acted upon by means for imparting to it a return force in order to restore the armature to its non-attracted position, but in Fig. l such means are not shown. The armature 8 is provided with a pin 21, oiset from the armature shaft I0, which pin projects through an arcuate slot 26 formed in a cover plate 1 forming a removable part of the stator. The plate 1 should be as dust-tight as practicable. The pin' 21 extends to the exterior of the device and constitutes a means whereby power can 'be transmitted from the armature to a part to be operated by the electromagnetic device. In such an arrangement, it is neithernecessary to extend the armature-shaft I0 to the exterior of the device nor to provide for the shaft I0 a bearing in the cover plate 1, since the armature can be entirely supported by the stator core to be hereinafter described.

The armature is sli/own in Fig. l in its nonattracted position. It will be clear that, when the armature occupies its attracted position in which each pole 9 registers with a pole I1, the poles 9 practically illl or bridge the annular space between the body of the armature and the stator poles I1. y

They poles according to Fig. 1 are such that the lines of force pass wholly or mainly in a 6b radial direction from pole to pole. Ii desired, the arrangement may be such that the lines of force pass not only radially but also axiallythat is, in a direction substantially parallel to the axis about which the armature turns-and suitable arrangements are illustrated by Figs. 2 and 3, respectively. According to Fig. 2. the fluxpassing face of each stator pole is formed like a step, and according to Fig. 3 the face o! each stator pole is formed like a double step, in each instance each armature pole being stepped in counterpart to the corresponding stator pole. Such step-formed poles present a large eiiective surface for the radial and axial emission and reception of the magnetic ux.

In Fig. 2 there is also shown a portion of a bearing I6 which is interposed between the discform armature l and the stator core 3, only partially shown. This bearing consists of a circular thrust ball-race surrounding the armature-shalt II, and it can be made large enough in diameter to ensure that such tilting forces to which the armature may be subjected in the operation of the device are taken up and withstood satisfactorily by the bearing. An additional bearing is provided in the cover plate 1 for the armatureshaft I0.

Referring to Fig. 4, it will be seen that the stator is made in the form of a pot, the annular wall of which consists of a ringlike yoke I and the base oi' which consists of a member 3a made in one piece with the core 3 of the stator. The core 3 and base 3a constitute a holder for a coil 4 constituting the magnet-held winding which preferably is withdrawably mounted on the core. The stator yoke I, which bears the poles I1, has a marginal flange Ia to which the member la is peripherally attached. The winding I is square in cross-section.

In this construction, the armature-shaft consists of an integral boss I0 on the disclike armature body 8 and a journal II extending into and journalled in a bore I2 which axially penetrates the core 3. A thrustbearing I I is provided to take up and withstand any axial stress to which the armature 8 may be subjected in the operation of the device; and the bearing may consist of one or more balls, although only a single ball is shown. The armature can be axially adjusted relatively to the stator through the intermediary of the ball-bearing I4 by a screw-adjustment ball-support 24 screwed into the core 3. As in the construction according to Fig. 2, a bearing I6 is provided. The bearing I6 is shown as ballbearing, but any other form of bearing may be employed instead; for example, a sliding-face bearing.

The stator and armature are dimensionally so designed that their ilux-conducting portionsnamely, the core 3, the base 3a, the yoke I, the poles I1, the poles 8 and the armature body loffer to the circulating tlux a path whose crosssectional area is practically constant, or nearly' so. Moreover, the said cross-sectional area is suiliciently large in relation to the ampere-turns of the iield winding to ensure that the stator and armature cannot reach their saturation limit in the ordinary operation oi' the device.

The armature-shaft III extends through the cover-plate, and has secured to it, outside the plate 1, a lever arm 30. As can be seen best in Fig. 5, the arm l0 is provided with a roller 3| which engages with a curved cam surface of a lever I2 whose fulcrum bolt 2l is secured to the plate 1. The lever 32 is acted upon by a return spring Il, which serves to return the amature to its non-attracted position whenever the magnet is de-energised. The arrangement is such that the to-and-irom angular motion of the armature I, arm 3l and lever I2 is transmitted to and converted into rectilinear motion of a relay-actuating member 31.

'I'he plate 1 is adapted to be secured to an instrument panel or wall, tor which purpose the plate has screw-holes 34.

The multi-contact relay to which the electromagnetic device is applied is of such a nature that the device serves to switch-in and switch-out the contacts. An eight contact relay has been shown, involving the use ot four upper terminals and four lower terminals all denoted by 3l. To these terminals the outer electricity conductors (not shown) would be connected in the usual manner. The electromagnetic device and the relay are preferably mounted as a single structural unit on the plate 1. In order to minimise the power required to operate the relay, contacts or bridges consisting of rollers Il can be employed with advantage as the means whereby current is passed between the respective terminals.

The poles l and I1 have been illustrated as of the same double-step form as in Fig. 3, but it is to be understood that they may have any other suitable i'orm, for example axial or unstepped form, as illustrated by the other gures of the drawings.

To maintain the desired constancy oi crosssectional area, the core base la thickens on its outer face towards the centre.

Referring to Fig. 6, the pot-formed body or pot" of the stator therein shown is of such a nature that it can be made by a stamping process or by a drawing process from a single piece. the poles I1 being formed at spaced intervals around the outer edge of the pot by a hanging operation.

To improve the magnetic conductability between the core l and the pot and to preserve constancy in the cross-sectional area oi.' the magnetic circuit, discs l and 8 with nattish-coned inner faces are secured to the core. The cover plate 1 is slipped upon the outermost rim of the POt.

To provide for axial adjustment o! the armature l in relation to the stator, distance pieces 2| are inserted between the thrust-ball Il and the closed end of the bore I2.

The armature l also may be of such a nature that it can be made by a stamping process or by a drawing process.

Referring to Figs. 'I and 8, the armature therein shown is composed of laminae, which may be stampings. 'Ihis is the preferred form of armature, and such an amature may be used with advantage in any of the other constructions herein described. There are also provided nattish-coned discs B and I, but these are turned out of the same piece as the core 3, so that the core presents the appearance oi' an ordinary yarn or thread bobbin. The pot is provided with an out-turned ilange Ib andto this flange there is attached as a separate part a crown-like ring I5 on which the poles I1 are formed. It is not necessary for the armature-shaft II to be a neat nt in the bore I2, because a stub Il and bearing I9 can be provided which take up any tilting stresses to which the armature is subjected. An advantage oi providing such a bearing is that the need for accurate nt between the shaft I I and the bore I2 is avoided.

Referring to Figs. '1 and 9, the armature shaft I I in each instance is shown provided with a stub I8 which abuts against av thrust ball I 4 located in a small cavity into which the stub I8 extends and with which it forms a bearing. In Figs. '1 and 9, the said cavity is constituted by a bore I9 which is a continuation of, but smaller in size than, the main bore I2. 'I'he arrangement is such that the stub I8 serves to take up any tilting forces to which the armature and its shaft may be subjected. The friction losses of such a bearing are small.

Referring to Fig. 10, the armature 8 is lo-` cated radially within the ring of poles I1 on the pot constituting the main body of the stator, and the bearing I6 is constituted as a ball-bearing. As in Figs. 4 and 9, a screw 24 is provided for axially adjusting the armature in relation to the stator.

Referring to Fig. 11, in this construction the armature 8 is disposed between two cores 3 respectively embraced by windings 4. The exterior portions of the stator are constituted by two pot-form caps Ic and Id between which is sandwiched the ring I5 on which are formed the poles I1. The arrangement is such that the stator constitutes a conductor for two magnetic Iiux circuits. Such an arrangement has a higher efficiency in as much -that the armature works in a space enclosed by two magnetic fields practically not subject to loss by straying. The armature is disposed in the zone between the cores 3, and if desired ball, roller or other anti-friction bearings may be employed to support the armature-shaft in the respective cores. In this construction one is concerned wholly or mainly with radial stresses. One of the cores 3 is completely penetrated by its bore l2 to provide a passage to the exterior of the device for the armature shaft I0.

Features already described with reference to the preceding figures, more especially Figs. 4, 6 and 7 can also be applied to a two-field arrangement such as illustrated by Fig. 11.

Although it is only in Figs. 4 and 5 that a return spring 33 has been shown, it is to be understood that4 equivalent return means would be provided in each of the other constructions herein described and illustrated.

In the constructions according to Figs. 6 to 8, the armature 8 is axially spaced from the stator poles I1; whereas, in the constructions according to Figs. 10 and 1l the armature 8 is arranged radlaily within the ring of working poles I1. In the constructions according to Figs. 2, 3 and 4, the armature 8 is spaced both axially and radially from the stator poles I1.

In order to attain the highest efliciency, it is necessary that the winding space should be fully occupied. Figs. 12 and 13 illustrate a difference between a winding composed of circular section wire and a winding composed of square section wire. By employing wire of which the cross section is so chosen that useless air spaces are avoided, one can obtain considerably more turns of' wire in comparison with what one would obtain by using circular section wire of the same crosssectional area. Thus, one can with advantage use wire of which the cross section is of such a geometrical form that the sides of adjacent and superposed wires fully cover or register with one another.

For winding material it has been proposed heretofore, to use, inter alia, aluminium or alloys thereof as a suitable substitute for copper, the material used to be given an insulating surface'or somcorresponding surface modification. As will be manifest, aluminium can only be employed as a complete substitute for copper if the number of turns is proportionately increased, or if at the outset the prescribed sizes are exceeded. By using wire of the cross section indicated (for example in Fig. 13) useless air spaces such as shown in Fig. 12 between adjacent turns of the wire will be avoided and accordlinglythe required extra turns -of aluminium or the like can be accommodated in the same winding space, and the dimensions which would be prescribed for a winding composed for circular-section copper wire need not be exceeded. Accordingly, it is to be understood that, in any of the constructions of the electromagnetic device herein described and illustrated, the wire used for the field winding or windings may be of the cross-sectional form illustrated by Fig. 13.

I claim:

1. An electromagnetic device comprising a stator formed about a central axis and provided with an axial core, a central bore in said core, a field winding on said core, an armature constituted by a disc-like body on a shaft journalled insaid bore, said armature being adapted to turn to-andfro in the stator about said axis under electromagnetic action of the stator andthe opposed action of armature-returning means, angularly spaced toothlike pole-projections on the stator, similarly angularly spaced toothlike poleprojections on the armature, said stator and armature being spaced apart axially to leave an interpole gap, an abutment in said bore, a thrustbearing between said abutment and said shaft, said abutment being adjustable in said core to effect axial regulation of the armature in relation to the stator and therefore regulation of said gap.

2. An electromagnetic device comprising a stator formed about an axis and including an annular wall with a base and an axial core, stator poles on said wall presenting magnetic-flux conducting faces which face forwardly away from said base and a field winding upon said core and within said wall, an armature journalled for ro-` tation about said axis and arranged in front of said stator, poles on said armature presenting magnetic-flux conducting faces which face to- Wards said base, the faces presented by said armature and its poles being axially spaced from the faces presented by said stator and its poles, said faces being arranged in planes to which said axis is perpendicular, said stator and armature poles being adapted to interact magnetically to rotate said armature whenever said winding is energised, means for returning said armature whenever said winding is de-energised, and means for regulating the axial spacing between said stator and armature.

3. An electromagnetic device comprising a stator formed about a central axis and constituted by a pot with a disc-like base and a circular wall, a rim flange on said wall, a short heavysection central core secured to said base and extending therefrom axially and internally of said pot, a series of angularly spaced stator poles on said flange, said poles projecting axially in front of said flange, and a field winding on said core, an armature journalled for rotation about said axis and arranged in front of said stator, poles on said armature presenting magnetic-flux conducting faces which face towards said base, said faces being arranged in a plane to which said axis is perpendicular, said armature and its poles being axially spaced from said stator and its poles, said stator and armature poles being adapted to interact magnetically to rotate said amature whenever said winding is energised, means for returning said amature whenever said winding is deenergised. and means for regulating the axial spacing between said stator and armature.

4. An electromagnetic device comprising a stator formed about an axis and including an annular Wall with an axial core, stator poles on said wall facing forwardly away from said wall and a field winding upon said core and within said wall, a shaft journalled in said core for rotation about said axis and extending forwards from raid core, an armature comprising a body of disc-like formation secured to said shaft and provided with angularly spaced radially projecting amaturepoles, said body and armature-poles being in front of but spaced from said core and statorpoles so as to leave a small axial airgap, said amature-poles being attracted by said statorpoles to rotate said armature and shaft about said axis whenever said winding is energised, means for returning said armature and 'shaft whenever said winding is de-energised, and means for regulating the axial size of said air-gap.

5. An electromagnetic device comprising a stator formed about an axis and constituted by an annular wall, an axial core and a base interconnecting said wall and core, stator poles on said wall facing forwardly away from said base, and a field winding upon said core and within said wall, an armature journalled in said core for rotation about said axis and arranged in front of said stator, poles on said armature facing towards said base, said armature and its poles being axially spaced from said stator and its poles to leave an air-gap, said stator and armature poles being adapted to interact magnetically to rotate said armature whenever said winding is energised, means for returning said armature whenever said winding is de-energised, a thrustball bearing to take rearward axial thrust due to the magnetic interaction between said stator and armature, said bearing being arranged in4 said core and applied to said armature, and an abutment for said bearing, said abutment being screwed into said core and being adjustable axially thereof to axially displace said armature to regulate the axial size of said air-gap.

6. An electromagnetic device comprising a stator, angularly spaced poles on said stator, a

field winding on said stator, an armature rotatably mmmtod in relation to said stator, angulariy spaced poles on said armature. said armature being spaced from said stator so as to leave a small airgap,athrustbearingtotakerearwardaxial thrust due to magnetic inter-action between said stator and armature, and an abutment for said bearing, said abutment being screwed into said stator and being adjustable to displace said armature to regulate the size of said air-gap.

7. An electromagnetic device comprising a stator formed about an axis and having for its components an annular wall, an axial core, a base interconnecting said wall and core, and stator poles on said wall facing forwardly away from said base, a iield winding upon said core and within said wall, an armature iournalled on said stator for rotation about said axis and arranged in front of said stator, poles on said armature facing towards said base, the faces of said stator and rotor poles respectively being arranged in transverse mutually parallel planes, said armature and its poles being axially spaced from the stator and its poles, said stator components and s said amature all being made of magnetism-conducting material and being adapted to interact magnetically to rotate said amature whenever said winding is energised, and means for returning said armature whenever said winding is deenergised.

8. An electromagnetic device comprising a statorformed about a central axis and having for its components a pot with a disc-like base and a circular wall, a rim flange on said wall, a short heavy-section central core secured to said base and extending therefrom axially and internally of said pot and a ring of angularly spaced stator poles secured to said flange, said poles projecting axially in front of said ring, a iieid winding on said core, a shaft iournalled in said core for rotation about said axis and extending forwards from said core, an armature having for its components a body of disc-like formation secured to said shaft and angularly spaced radially proiecting amature-poles on said body, said body and armature-poles being in front of but spaced from said core and stator-poles so as to leave a small axial air-gap, said stator components and armature components being made of magnetism-conducting material and being adapted to interact to rotate said armature about said axis whenever said winding is energised, and means for returning said armature whenever said winding is deenergised.

HEINRICH LIST. 

